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990

Appendix V.

on a plate N which fits truly in circular V grooves p, and which
may be rotated by the ratchet feed so that during rotation the
upper end Q will remain at a constant height. But true rolling
also requires the spindle to revolve while slewing, which motion
is produced by the roll cone R (which is part of a true cone).
Fig. 913 shews two views of the roll cone R, where s s is the base
of cone of which R is a part, while T T the blank forms the
opposite cone, and it follows that a true rolling of R will produce
a true rolling of A. The revolution of B is secured by the
coupling of K to B at u, and the true rolling of R without slip is
obtained by connecting two steel bands vv to the brackets ww,
which are fastened to points x x on the roll cone, the latter being
supported at the correct height by the block Y. In practice, after
choosing a suitable roll cone (of which twenty-two are supplied
with each machine) for the particular angle of wheel, the cone
and spindle are lowered at Y by one degree, such an adjustment
giving a rather more rounded tooth and conducing to smoother
action when the wheel is in use.

The lateral feed, as already mentioned, is obtained from
rod H, which rotates the ratchet wheel z, shaft a, pinion b, and
the sector on plate N. Reversal is produced by the hand knob^/5
which couples either bevel pinion to shaft a by a clutch at *, and
the handle g serves for hand feed or for setting. Depth feed is
provided at h^ where the turning of the screw will raise or lower
the frame/ round the fulcrum q, and thus simultaneously raise or
lower the blank, the exact depth of tooth being read on the
wheel h.

The dividing or pitching apparatus is seen at £, Figs. 911 and
913. It consists of the usual dividing plate k on a worm spindle /
in gear with the worm wheel m. Between every complete cut the
tool is lifted and the blank spindle rotated by the amount of the
pitch.

The Working of the Machine.—After putting in the proper
roll-cone, and setting to correct angle both for blank and cutting
tool, the blank is lowered by the wheel h, and the tool begins to-
cut out the centre of the interspaces, while a gradual feed is
being given at h, as shewn in Fig. 913, until the mid portion is
cut out to the correct depth. During this operation the roll feed